Self-propelled apparatus for applying markings to roads and the like



SELF-PROPELLED APPARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKENov. 11, 1969 J- HARDING ET AL 3,477,352

1969 J. HARDING ET AL 3,477,352

' SELFPROPELLED APPARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKEFiled Dec. 21, 1967 5 Sheets-Sheet 2 Nov. 11, 1969 J.-HARDING ET AL3,477,352

SELF'PROPELLED APPARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKEFiled Dec. 21, 1967 N ,1969 J. HARDING ET AL 3,477,352 SELF-PROPELLEDAPPARATUS FOR APPLYING MARKINGS T0 ROADS AND THE LIKE 5 Sheets-Sheet 4Filed Dec. 21, 1967 I Nov. 11, 1969 v J. mm; ETAL 3,477,352

SELF-PROPELL ARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKE FiledDec. 21, 1967 v 5 Sheets-Sheet 5 United States Patent 3,477,352SELF-PROPELLED APPARATUS FOR APPLYING MARKINGS T0 ROADS AND THE LIKEJohn Harding, Peter Placzek, and Sidney Glenroy Campbell, Rowfant, nearCrawley, England, assignors to Universal Highway (Contracting) Limited,Rowfant, near Crawley, England Filed Dec. 21, 1967, Ser. No. 692,515Claims priority, application Great Britain, Dec. 28, 1966,

7,982/66 Int. Cl. B05b 7/16, 9/06 US. Cl. 94-44 11 Claims ABSTRACT OFTHE DISCLOSURE The present invention relates to a method of applyingmarkings in the form of continuous or discontinuous lines on thesurfaces of roads or the like and is also concerned with self-propelledroadmarking apparatus for use in carrying out this method.

The invention has for its object to enable such markings to be appliedalong a road surface or the like at speeds of up to miles per hour.

According to the invention a road-marking apparatus includes a vehiclehaving mounted thereon a spray gun arranged for spraying a moltenthermoplastic road-marking material onto a road surface beneath thevehicle to form a coating thereon in the form of a strip, means forstoring the thermoplastic road-marking material on the vehicle in amolten state and maintaining its temperature within a predeterminedlimits through its travel to the outlet of the spray gun, an aircompressor on the vehicle for delivering air under pressure to effectthe transfer of the thermoplastic road-marking material from the storingmeans to and its discharge from the spray gun, means on the vehiclemounted behind and in alignment with the spray gun for sprayingreflective material over the strip of thermoplastic material before thestrip cools and sets, and means for controlling the operation of thespray gun.

A further spray gun may be arranged for spraying an adhesive materialonto the road surface in advance of the first said spray gun and in theform of a strip which is wider than the strip of thermoplasticroad-marking material.

The further spray gun may be provided with means for adjusting itsposition transversely of the path of travel of the chassis so as toenable the strip of adhesive material applied by it to be correctlyaligned with the strip of thermoplastic road-marking materialsubsequently applied.

The thermoplastic road-marking material may be that forming the subjectof copending patent application No. 655,345. In practice, the latter isadapted to be discharged from its spray gun at a high temperature, e.g.,at a temperature in the region of 400 F., so that heat fromthermoplastic material deposited on the adhesive coating will drive offsolvents from the latter.

The interval between the time when a given point on the road surface iscoated with the adhesive material and ice the time when the road-markingmaterial is subsequently applied over the adhesive coating covering thesame point is preferably not less than 1 second.

The width of the strip of adhesive material applied to the road surfaceis advantageously at least 2 inches wider than the superimposed strip ofthermoplastic road marking material.

Preferably, loose foreign matter such as dust and surface water isremoved from the road surface by a high pressure air jet locatedimmediately in advance of the first spray gun. Alternatively, a rotarybrush or sponge roller may be used for this purpose.

Thus there is provided a method of marking a road surface comprising thesteps of spraying a moisture-repellant, solvent-based adhesive materialonto the road surface to form thereon a strip-like coating of saidadhesive material, spraying over said coating of adhesive material amolten thermoplastic road-marking material to form a strip-like roadmarking of smaller width than the said coating of adhesive material andspraying reflective media over the strip of thermoplastic roadmarkingmaterial before said strip of road-marking material cools and sets.

A control panel may be provided on the rear part of the chassis, whichcontrol panel incorporates switches for controlling the operation of themelting and storing apparatus as well as the operation of the furtherspray gun and the reflective material spraying means.

The panel may incorporate a rotary switch for selecting the pattern tobe applied to the road surface from a number of alternative patterns,this rotary switch being connected in an electrical control circuitincluding a pulse counter to which pulses are transmitted from apulse-transmitting tachometer driven by a wheel in contact with theground and adapted to actuate a control switch in the operating circuitof the solenoid valve. Conventional circuit techniques are used toarrange that the valve is on and off for selected numbers of pulses fromthe tachometer.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevation of a self-pro pelledroad-marking apparatus,

FIG. 2 is a diagrammatic plan view of the apparatus shown in FIG. 1,

FIG. 3 is a block diagram of the circuits for compressed air,thermoplastic road-marking material, and reflection material in theapparatus shown in FIG. 1,

FIG. 4 is a block diagram of the heating system of the apparatus shownin FIG. 1,

FIG. 5 is a "block diagram of the electrical control circuitry of theapparatus of FIG. 1,

FIG. 6 is a diagrammatic side elevation of a further self-propelledroad-marking apparatus in which parts corresponding to those shown inFIGS. 1 and 4 are given corresponding reference numerals, and

FIG. 7 is a diagrammatic plan view of the apparatus shown in FIG. 6.

Referring to FIGS. 1 and 2 of the drawings, the various component partsof the road-marking apparatus are all mounted either on a large sizelorry chassis of conventional design or on a guide arm 11 connected tothe front end of this chassis. The guide arm 11 is provided at its frontend with a castor wheel 12 and is pivotably connected at its rear end tothe chassis so that it can be swung up into the position indicated inbroken lines at 11 in FIG. 1 when not in use. As can be seen in FIG. 2,the guide arm 11 is connected to the front end of the chassis at a pointclose to the near side thereof and extends forwardly from this point ata small angle in the direction towards the near side. A bracing arm 13has its rear end mounted for pivotal movement about a horizontal axisaligned with the pivotal axis of the guide arm 11 and has its front endconnected to a split collar clamped around the guide arm 11approximately midway between the front and rear ends of the latter.

The chassis is provided with a drivers cab 14 within which are provideddual steering, braking, accelerator and like controls, i.e., twocomplete sets of such controls are provided respectively on the offsideand nearside.

Mounted on the chassis close behind the drivers cab 14 is an aircompressor unit 15 driven by a diesel engine and adapted to supplycompressed air at 100 p.s.i. Three further units are mounted one behindthe other on the part of the chassis to the rear of the air compressorunit 15, namely a melting and storage unit 16 for thermoplasticroad-marking material, a pressurized container 17 for reflectivematerial, and a control panel 18.

The melting and storage unit 16 includes a container 37 (FIG. 4), fittedwith a heat-exchanger 38 by which thermoplastic road-marking material inthe container 37 is heated up to 400 F. For this purpose, mineral oil isheated by a Beverley heater 39 and continuously circulated throughmelter racks which are arranged within the container 37 and constitutethe heat-exchanger 38. Molten thermoplastic road-marking material istransferred alternately to two jacketed pressure-storage vessels (shownschematically as a unit 40 in FIG. 4) located beneath the container 37at a rate of two tons per hour.

The pressurized container 17 shown in FIGS. 1 and 2 is designed forstorage of reflected material such as Ballotini beads at a pressure ofup to 30 p.s.i.

The control panel 18 is arranged so that it can be operated by a personseated either on a near-side seat 19 or on an off-side seat 21.

Mounted on the guide arm 11 a short distance behind the castor wheel 12is a device 22 for delivering a jet of air downwardly onto the roadsurface beneath it. The supply of compressed air to this device 22 fromthe compressor unit 15 is controlled from the drivers cab 14 by controlmeans operated by the driver.

Immediately behind the device 22 is a spray gun 23 for spraying anadhesive agent on the road surface. This spray gun 23 is adjustabletransversely to enable the strip of adhesive deposited thereby to bealigned with the markings applied subsequently by guns 24, 25 describedmore fully later. The spray gun 23 is adapted to be supplied with atack-coating material from an airpressurized container 20. The supply ofthis material to the spray gun 23 is controlled by .a solenoid-actuatedvalve operable by a person seated at the control panel 18.

The guns 24, 25 are mounted on a carriage 26 which is provided at itsleading end with a castor wheel 27 and is connected by parallel links 28to a supporting bracket 29. The bracket 29 is fixed to a transverseslide 31 by which it can be moved into appropriate positions fornearside, centre or off-side marking.

The gun 24 is adapted to be supplied with molten thermoplasticroad-marking material from the melting and storage unit 16 via jacketedpipes. Heated mineral oil from the heat-exchanger of the unit 16 iscirculated through the jacket spaces of these pipes so as to maintain aminimum temperature of 400 F. at the nozzle mouth of the gun 24.

The gun 25 is connected by pipes to the pressurized container 17.

The guns 23, 24 and 25 have been described above as single guns, butwhen it is required to spray a road width of more than 6" in width, eachsuch single gun would in practice be replaced by two or more gunslocated sideby-side.

Pipes 41, 42, 43, 44 and 45 shown in FIG. 3 supply compressed air fromthe compressor 15 to the gun 22, the container 20 for adhesive, thepressure vessels 40,

the container 17 for reflective material and to a control valve 46, andto the guns 24 and 25, respectively.

The control valve 46 is of the conventional type in which theapplication of a predetermined air pressure to one side of an actuatingmember causes the actuating member to move and so open the valve toallow, in the present case, molten thermoplastic road-marking materialto flow through the valve, removal of the predetermined air pressurecausing the valve to close.

Each of the guns 24 and 25 incorporates a control valve of the typedescribed herein before, application of the predetermined air pressureto the control valve of the gun 24 enabling the molten thermoplasticroad-marking material to flow through the gun 24, and application of thepredetermined air pressure to the control valve of the gun 25 enablingthe reflective material from the container 17 to flow through the gun25.

Compressed air for driving the molten thermoplastic road-markingmaterial from the pressure vessels 40 and the reflective material fromthe container 17 is obtained from the compressor 15 by way of the pipes43 and 44 respectively.

The application of the predetermined air pressure to the control valve46 is controlled by a solenoid-actuated valve 48.

Another solenoid-actuated valve 47 controls the release of air pressurein the pressure in the pressure vessels 40 to the atmosphere. Inoperation, the valves 47 and 48 are actuated to allow moltenthermoplastic roadmarking material to flow from the container 37 undergravity to the pressure vessels 40, the control valve of the gun 24being closed. The valves 47 and 48 are then closed and pressure buildsup to a predetermined valve in the pressure vessels 40.

A third solenoid-actuated valve 49 controls the supply of compressed airto the control valves of the gun 24 and 25. Energisation of the splendidsolenoid 50 of the valve 49 will be described hereinafter in more detailwith reference to FIG. 5.

It will be apparent that for each further pair of guns for sprayingroad-marking material and reflective material respectively, a furthersolenoid-actuated valve will be required.

Two further solenoid-actuated valves 51 and 52 control the flow ofadhesive from the container 20 to the gun 23 under the pressure appliedthrough the pipes 42, and the supply of compressed air to the gun 22,respectively.

The heating system for the thermoplastic road-marking material will nowbe described with reference to FIG. 4.

In the heater 39, mineral oil is heated to a temperature of 400 F., theheater being thermostatically controlled to maintain the mineral oil atthis temperature.

The mineral oil passes out of the heater 39 by way of a pipe 53 andreturns by way of a pipe 54 under the action of an electric pump 55. Therate of working of the pump 55, and hence the rate at which the mineraloil is circulated, is controlled by a thermostat 56, located in thecontainer 37 in which the thermoplastic road-marking material is melted,which controls the power supply 56' of the pump 56,

The pipe 53 includes a temperature-sensitive three-way valve 57 whichallows the mineral oil to flow through heater-jackets 58 surrounding thepressure vessel 40 only when the temperature of the plasticizerthermoplastic road-marking material is below 400 F., the valve 57otherwise operating to direct the minerial oil through a by-passpipe 59which conveys the mineral oil to a like temperature-sensitive three-wayvalve 60 at the outlet of the temperature jackets 58.

Two further temperature-sensitive three-way valves 61 and 62 determinewhether the mineral oil flows through the jackets 63 and 64 of the pipeand the gun 24 or through a further by-pass pipe 65.

The mineral oil finally passes through the heat-exchanger 38 in thecontainer 37 before entering the pump 55. The container 38 is preferablyprovided with a jacket (not shown) having an associated by-pass pipe(not shown) through which the mineral oil may pass.

From FIG. 1 it will be seen that a short distance in front of the rearwheels of the chassis, there is arranged a skip liner indicatedgenerally at 32. This skip liner has a wheel 33 which is adapted, whenthe skip liner is in operation, to be rotated by contact with the roadsurface. A disc 34, which is belt-driven by the wheel 33, carries a ringof magnets which is arranged to cooperate with a reed switch 35connected by leads 36 in an electronic circuit containing a pulsecounter (FIG. 5). A rotary switch (shown in FIG. 5) mounted in thecontrol panel 18 is used for selecting the pattern to be applied to theroad, e.g. either a continuous line or an interrupted line consisting ofline markings of predetermined lengths alternating with gaps ofpredetermined lengths. The pulses from the reed switch are counted in amanner determined by the setting of the rotary switch and the resultingsig nals are issued to operate a solenoid-actuated valve which controlsthe supply of compressed air to the valves in the guns 24 and 25.

In FIG. 5 the rotary switch is shown as two rotary switches 70 which inpractice are ganged together. The circuit shown in FIG. 5 includes asource 71 of electric power connected to one contact of the reed switch35, the other contact of the reed switch 35 being connected to the fixedcontact of a manually operable two-position switch 72 mounted in thecontrol panel 18. When the disc 34 rotates at a steady rate, the reedswitch opens and closes regularly and thus when the switch 72 is in theposition shown a regular train of pulses is applied to the inputconnection of a first monostable multivibrator circuit 73 which servesas a pulseshaper. In one embodiment the interval between two pulsesapplied to the monostable circuit 73 corresponds to an advance of sixinches by the vehicle. The output of the monostable circuit 73 isapplied through respective capacitors 74 of equal capacitance to theinput connections of two further monostable multivibrator circuits 75and 76. In a pattern-depositing operation, only one or the other of thecircuits 75 and 76 produces output pulses at any time. The outputconnections of the monostable circuits 75 and 76 are respectivelyconnected to the input connections of two pulse-frequency dividingcircuits 77 and 78 including respective capacitors 79 and 80. Each ofthe circuits 77 and 78 is of the type in which the respective capacitor,79 or 80 as the case may be, is charged in steps, corresponding to inputpulses, up to a predetermined voltage at which a discharge circuit forthe capacitor opens and the capacitor discharges rapidly, therebyproducing a pulse at the output connection of the pulse-frequencydividing circuit. Thus, in operation when, for example, the monostablecircuit 75 is producing output pulses, the capacitor 79 is charged insteps by these output pulses until the predetermined voltage is reachedwhereupon the capacitor 79 discharges rapidly and the pulse-frequencydividing circuit 77 applies a short pulse to one input of a bistablemultivibrator circuit 81 which serves a control switch. When operating,the monostable circuit 76 and the pulse-frequency dividing circuit 78co-operate in the same manner to supply a short pulse to the other inputof the bistable circuit 81. Thus the monostable circuits 75 and 76 withthe pulse-frequency dividing circuits 77 and 78 act as a counter. Thebistable circuit 81 changes from one of its states to the other wheneverit receives an input pulse from the circuit 77 or from the circuit 78since it is arranged that such inputs are ap plied alternately, as willbe apparent from the following description.

On output connection of the bistable circuit 81 is connected to theinput connection of an amplifier 82 of which the output connection isconnected to one contact of a manually operable switch 83 mounted in thecontrol panel 18. The other contact of the switch 83 is connected to onefixed contact of a manually operable three-position switch 84. Themovable contact of the switch 84 is connected to the solenoid 50, sothat when the movable contact of the switch 84 is in the position shownin FIG. 5 the solenoid 50 is energised when the bistable 81 is in one ofits states and is de-energised when the bistable 81 is in the other ofits states.

The energisation of the solenoid 50 can also be controlled manuallysince the other fixed contact 85 of the switch 84 is connected to thepower supply 71. In controlling the energisation of the solenoid 50manually, the movable contact of the switch 84 is placed in contact withthe fixed contact 85 to energise the solenoid 50, and is placed in itscentral position, at which it is in contact with neither of the fixedcontacts, to de-energise the solenoid 50.

An indicating light 86 is provided at the output connection of theamplifier 86 to indicate the presence of an output from the amplifier86.

Where more than one gun for the thermoplastic roadmarking material andone gun for the reflective media is provided, further solenoids 87 withassociated three-position switches 88 are provided. For example, thereare shown in FIG. 5 two further solenoids 87, so that two further gunsfor the thermoplastic road-marking material and two further guns for thereflective media can be controlled by the circuit shown in FIG. 5. Itwill be apparent that, with a suitable amplifier 82 and source 71, asmany further solenoids 87 as desired may be added to the circuit shown.

Since the solenoid 50, when the switch 84 is in the condition shown, isenergised when the bistable circuit 81 is in one state and isde-energised when the bistable circuit 81 is in the other state, theguns 24 and 25 are spraying when the bistable circuit 81 is in the saidone state and are not spraying when the bistable circuit 81 is in thesaid other state.

The output connections 89 and 90 of the bistable circuit 81 areconnected to the monostable circuits 75 and 76 respectively in such amanner that when the bistable circuit 81 is in one of its states themonostable circuit 75 is rendered inoperative and the monostable circuit76 is rendered operative, and that when the bistable circuit 81 is inthe other of its states the monostable circuit 75 is rendered operativeand the monostable circuit 76 is rendered inoperative. The relationshipbetween the input connections and output connections 89 and 90 of thebistable circuit 81 is so arranged that, for example, when themonostable circuit 75 is operative and the pulse-frequency dividingcircuit 77 consequently eventually applies a pulse to the bistablecircuit 81, the application of that pulse causes the monostable circuit75 to be rendered inoperative and the monostable circuit 76 to berendered operative. It will be realised that in this way one of themonostable circuits 75 and 76, say circuit 75, is operative when theguns 24 and 25 are spraying, and the other, circuit 76, is operativewhen the guns 24 and 25 are not spraying. The number of pulses from thereed switch 35 during which the monostable circuit 75 remains operativeis dependent upon the number of output pulses from the circuit 75required to cause the capacitor 79 to be charged up to the predeterminedvoltage. The predetermined voltage is fixed and thus the lengths of theoutput pulses from the circuit 75 determine the number of such pulsesrequired. The time constant and hence the lengths of the output pulsesproduced by the circuit 75 is arranged to be variable by means of therotary switch 70, as will now be explained.

The monostable circuit 75 is connected through a manually operabletwo-position switch 91 having its movable contact biased into theposition shown to a source of variable voltage 92 incorporating therotary switch 70. Each position of the rotary switch 70 corresponds to adifferent one of a plurality of difierent voltages and hence, by virtueof a manner of connection of the switch 91 to the monostable circuit 75well known to those skilled in the art, to a different one of aplurality of different time constants of the monostable circuit 75.

The number of pulses from the reed switch 35 during which the monostablecircuit 75 will remain operative can therefore be set at any one of aplurality of different valves by means of the rotary switch 70.

A switch 93 and a source 94 serve the same function in respect of themonostable circuit 76.

Thus the setting of the switches 70 determines both the number of pulsesfrom the reed switch 35 during which the guns 24 and 25 are spraying andthe number during which they are not spraying. In other words, thesetting of the switch 70 determines the length of the road marksdeposited and the length of the gaps between successive road marks.

Two sources 95 of resetting voltages are connected to respective fixedcontacts of the switches 91 and 93 for resetting the monostable circuits75 and 76. Two switches 96 and two switches 97 are also connected to thesources 95. Momentary closure of one of the switches 96 resets thebistable circuit 81 in one of its states, which state depending uponwhich of the switches 96 is momentarily closed. Momentary closure of oneof the switches 97 causes the capacitor of the associatedpulse-frequency dividing circuit to be charged to the predeterminedvoltage. In practice, the switch 91 is ganged to one of the switches 96and to one of the switches 97, the switch 93 being ganged to the otherswitches 96 and 97 and the arrangement being such that by momentarilyturning the movable contact of the switch 91 to its reset position, thewhole circuit is set into a condition corresponding to, say, the startof the deposition of a road mark, and that similar use of the switch 93sets the whole circuit into a condition corresponding to the start ofthe gap between successive road marks. The details of such anarrangement will be apparent to those skilled in the art and thereforeare not further described herein.

A manually operable switch 98 mounted on the control panel 18 and setopen, as shown, when a road-marking operation is in progress is providedto enable the functioning of the control circuit to be checked visuallyby means of observation of the light 86. To carry out such checking, theswitch 72 is turned to its other position, thus connecting the switch 98to the monostable circuit 73 and disconnecting the reed switch 35therefrom, and the switch 83 is opened to prevent accidental operationof the spray guns 24 and 25. The switch 98 is then closed repeatedly tosimulate operation of the reed switch 35. By counting the number ofsuccessive closures of the switch 98 during which the light 86 remainsenergised and then those during which the light 86 remains de-energised,it is possible to ascertain whether the control circuit is operating inaccordance with the intended functioning determined by the setting ofthe rotary switches 70.

It will be apparent that the disposition of the magnets on the wheel 34must be arranged to cause the reed switch 35 to open and close in asprecise a manner as possible on rotation of the wheel 34.

The road wheel 33 which drives the disc 34 may also advantageously beused to drive a speedometer adapted to give accurate measurement of thespeed of the vehicle over the range of low speeds, for example up to tenmiles per hour, in which road-marking operations are effected. Thedriver of the vehicle can then more readily maintain a steady speedduring such operations.

An electric circuit (not shown) for energising the solenoid of thesolenoid-actuated valve 52 (FIG. 3) is controlled by a switch accessibleto the driver of the vehicle.

Further electric circuits (not shown) for energising the solenoids ofthe solenoid-actuated valves 47, 48 and 51 are controlled by manuallyoperable switches mounted in the control panel 18.

In operation, the vehicle is driven forward at a speed of between 5 and10 miles per hour, the driver taking care to ensure that he keeps asighting pin (not shown) on the front end of the arm 11 aligned with theroad markings to be renewed or with markings applied at intervals alongthe road to guide him. As the vehicle travels forward the various gunsare operated as follows.

The driver operates the gun 22 whenever necessary to remove dust orother foreign matter or free surface water from the road surface. If theroad surface is damp or covered with a frosty deposit, the operatorseated at the control panel 18 actuates the appropriate control to causea strip of adhesive agent to be deposited by the gun 23. The width ofthis strip will have been predetermined, by adjusting the height of thegun 23 above the road surface and, if necessary, by adding an additionalgun or guns, so that the width of the strip of adhesive applied will beapproximately two inches wider than the width of the road markingsubsequently to be applied by the guns 24, 25.

When the transverse slide is adjusted for off-side marking, the guidearm 11 must also be changed over to the off-side.

A suitable adhesive material may comprise a solution of a toughsynthetic elastomer in a medium which comprises at least one hydrocarbonsolvent in which the elastomer is readily soluble and at least onevolatile, non-flammable solvent of specific gravity greater than unity,the solution being of a sufficiently low viscosity to enable it to besprayed and the non-flammable solvent being present in sufiicient amountfor the solution to have a specific gravity greater than unity and anopen flash point above 75 F.

The adhesive material preferably also contains a cationic surface-activeagent, to bring abuot preferential wetting of a wet surface by thecomposition, with displacement of the water. Examples of such compoundswhich have proved very useful are long chain cyclic amines.

In preparing one example of an adhesive for use in the presentinvention, sufficient of a block copolyrner of styrene and butadiene(Cariflex Kl01-Shell Chemicals Ltd.) is added to an equal volume ofturpentine and trichloroethylene to produce a 10% solution by weight.For this purpose, every 2 gallons of solvent mixture requires 2 /2 lb.of the rubber. The mixture is stirred continuously with an efficientpaddle stirrer for several hours, until complete solution is obtained.To every 2 gallons of this solution is added 1 oz. of a long chaincyclic amine surfactant (Bitran H-Glover Chemicals Ltd.) which is wellstirred in, and the composition is then transferred to S-gallon drums.

FIGS. 6 and 7 show another embodiment of apparatus according to thepresent invention, which differs from the first described hereinbeforein that no container for melting the thermoplastic road-marking materialis provided on the chassis of the vehicle, the pressure vessel 40 havingtwo inlet-filling openings, each shown sealed by a lid 101, throughwhich molten thermoplastic road-marking material can be delivered froman ancillary vehicle (not shown) bearing apparatus for melting theroadmarking material. The vessel 40 incorporates a device (not shown)for stirring the molten thermoplastic roadmarking material therein, thedevice being driven by compressed air supplied by the compressor 15.

A container 102 for fuel, such as liquid petroleum gas, for the heater39, is mounted on the vehicle.

The operation of the guns 24 and 25 is controlled in the same manner asdescribed hereinbefore in relation to the embodiment shown in FIGS. 1 to5.

A device for delivering a jet of air downwardly onto the road surfacebeneath may be provided on the chassis of the vehicle shown in FIGS. 6and 7 at a position closer to the drivers cab 14 than the gun 24, theguide arm 11 of the previously described embodiment being dispensed within the case of this smaller vehicle.

lfurthermore, another ancillary vehicle carrying a pressurised supply ofadhesive and equipped with a spray gun corresponding to the gun 23 ofthe previously described embodiment may be employed to lay a trail ofadhesive before the vehicle shown in FIGS. 6 and 7.

It is preferable, for the purpose of obtained good reflection, inembodiments of the invention that, where the reflective material is inthe form of beads of transparent material such as Ballotini heads, themedia should be sprayed at a velocity sufficient to cause those beadswhich strike the surface of the thermoplastic material to become halfembedded in that material. Also, the beads should be sprayed in excessof the quantity required to cover the surface of the road marks sincethe excess beads which remain loose act as a sand and thus help toprevent the tread of the tyres of vehicles passing over the marks soonafter the deposition" from picking up the thermoplastic road-markingmaterial. It has been found, moreover, that the embedding of coolBallotini beads in the surface of a thermoplastic road mark enables aprotective skin of set thermoplastic material to form rapidly over themark.

Compressed air for use in atomising the adhesive and thermoplasticmaterials in the guns is, if required, obtained from the air compressor15, through supply lines (not shown) which include respective manuallyoperable valves accessible to a person seated at the control panel 18 atthe rear of the vehicle.

The spray gun 25 can be a conventional gun for spraying Ballotini beadsor the like.

We claim:

1. A road-marking apparatus, comprising:

a self-propelled, steerable wheeled chassis,

a guide arm projecting forwardly from said chassis,

a first downwardly directed spray gun mounted on said guide arm andarranged for spraying an adhesive material onto a road surface beneathsaid chassis to form a coating thereon in the form of a strip,

a second spray gun mounted on said chassis in a position near the rearend of the latter and in longitudinal alignment with said first spraygun and arranged for spraying a molten thermoplastic road-markingmaterial in the form of a narrower strip over the strip coating appliedby said first spray gun,

a container mounted on said chassis for storing said adhesive materialunder pressure,

means mounted on said chassis for melting said thermoplasticroad-marking material and storing it under ressure,

pipes connecting said container to said first spray gun and said meltingand storing means to said second spray gun,

means for maintaining the temperature of said thermoplastic road-markingmaterial within predetermined limits throughout its travel from saidmelting and storing means to the outlet of said second spray gun,

an air compressor mounted on said chassis for delivering air underpressure to effect the transfer of said adhesive material from saidcontainer to and its discharge from said first spray gun, as well as thetrans fer of said thermoplastic road-marking material from said meltingand storing means to and its discharge from said second spray gun,

control means for controlling the operation of said first and secondspray guns and means behind and in alignment with said second spray gunfor spraying reflective material over the strip of thermo-plasticroad-marking material applied by said second spray gun before said stripof road-marking material cools and sets.

2. Apparatus according to claim 1, wherein said control means includes:

a solenoid-actuated valve controlling the supply of compressed air fromsaid air compressor to said first and second. spray guns, and

manually operable switches on said chassis connected in the electriccontrol circuit of said solenoid-actuated valve.

3. Apparatus according to claim 2, wherein means are provided on saidguide arm in advance of said first spray gun for discharging a jet ofhigh-pressure air onto the road surface.

4. Apparatus according to claim 3, wherein there are also provided:

a road wheel connected to said chassis and adapted to be rotated bycontact with the road surface as the chassis advances,

a pulse-transmitting tachometer drivably connected to said road wheeland adapted to transmit pulses when driven by said road wheel,

an electrical control circuit,

a rotatary pattern-selecting switch connected in said control circuitfor selecting, from among a number of different road-marking patterns, aroad-marking pattern to be applied to the road surface,

a pulse counter connected in said control circuit and adapted to countthe pulses transmitted by said tachometer and to transmit signalsrelated to such pulse counting in a manner determined :by the setting ofsaid rotary switch, and

a control switch connected in the operating circuit of said solenoidvalve and arranged to control the opening and closing of said solenoidvalve in accordance with the signals transmitted by said pulse counter.

. A road-marking apparatus, comprising:

a self-propelled, steerable wheeled chassis, a spray gun mounted on saidchassis and arranged for spraying a molten thermoplastic road-markingmaterial on to a road surface beneath said chassis to form a coatingthereon in the form of a strip,

means mounted on said chassis for storing said molten thermoplasticroad-marking material under pressure, pipes connecting said storingmeans to said spray me a iis for maintaining the temperature of saidthermoplastic road-marking material within predetermined limitsthroughout its travel from said storing means to the outlet of saidspray gun,

an air compressor mounted on said chassis for delivering air underpressure to effect the transfer of said thermoplastic road-markingmaterial from said storing means to and its discharge from said spraygun,

means mounted on said chassis behind and in alignment with said spraygun for spraying reflective material over the strip of thermoplasticroad-marking material applied by said spray gun before said strip coolsandlsets,

control means for controlling the operation of said spray gun, saidcontrol means including:

a solenoid-actuated valve controlling the supply of compressed air fromsaid air compressor to said p y a road wheel connected to said chassisand adapted to be rotated by contact with the road surface as thechassis advances,

a pulse-transmitting tachometrical device drivably connected to saidroad wheel and adapted to transmit pulses when driven by said roadWheel,

an electrical control circuit connected to receive said pulses,

a pattern-selecting switch connected in said control circuit forselecting, from among a number of different road-marking patterns, aroad-marking pattern to be applied to the road surface,

pulse-counting circuit means connected in said control circuit andadapted to count the pulses transmitted by said tachometrical device andto transmit signals related to such pulse counting in a mannerdetermined by the setting of said rotary pattern-selecting switch to theoperating circuit of said solenoid-actuated valve to control the openingand closing of said solenoidactuated valve in accordance with the saidsignals transmitted by said pulse counter.

6. Apparatus as claimed in claim 5, wherein means are provided inadvance of said spray gun for discharging a jet of high-pressure air onto the road surface.

7. Apparatus as claimed in claim 5, wherein a further downwardlydirected spray gun is arranged for spraying an adhesive material on tothe road surface in advance of the first said spray gun and in the formof a strip which is wider than the strip of thermoplastic road-markingmaterial to be formed thereon,

a container is mounted on said chassis for storing said adhesivematerial under pressure, and

a pipe is provided connecting said container to said further spray gun,

said air compressor being adapted to effect the transfer of saidadhesive material from said container and its discharge from saidfurther spray gun.

8. Apparatus as claimed in claim 5, wherein a manually-operated switchis included in the operating circuit of the said electrically operablevalve and is arranged for overriding the said pulse counting circuitmeans and for controlling the said valve.

9. Apparatus as claimed in claim 5, wherein the said pulse-transmittingtachometrical device is adapted to generate one pulse for each advanceof six inches by the vehicle.

References Cited UNITED STATES PATENTS 2,026,870 1/ 1936 Dalton 94-442,076,370 4/1937 Hollinshead 94-44 2,357,930 9/1944 Clark 94-442,691,923 10/1954 Huck 94-44 3,018,704 1/1962 Searight 94-44 3,046,8547/1962 Wilson 94-44 3,262,375 7/ 1966 Eigenmann 941.5 3,326,098 6/1967Boettler 941.5 XR 3,356,261 12/1967 Stein 94-44 XR 2,430,534 11/ 1947Rodli.

JACOB L. NACKENOFF, Primary Examiner U.S. Cl. X.R.

